蛇纹石负载羟基磷灰石对矿区地下水中氟、铁和锰的动态吸附性能

Dynamic adsorption of fluoride,iron and manganese in underground water of mining area by Srp/HAP

针对矿区地下水中氟、铁、锰污染超标问题,利用湿法化学共沉淀法制备蛇纹石负载羟基磷灰石(Srp/HAP)复合吸附剂,通过动态吸附试验,研究Srp/HAP对F^(-),Fe^(2+),Mn^(2+)的同步吸附性能,考察吸附床高度、流速及进水质量浓度对穿透过程的影响。采用Adams-Bohart,Thomas模型拟合和SEM,EDS,XRD,BET,FT-IR等微观表征,分析Srp/HAP对F^(-),Fe^(2+),Mn^(2+)的吸附机理。结果表明,制备的Srp/HAP复合吸附剂颗粒紧实,既有Srp表面的片状卷曲结构,又解决了HAP表面团聚问题,负载后颗粒的比表面积、孔容均有明显增加,具有较好的表面孔隙结构,有利于氟、铁、锰的同步吸附去除。吸附柱吸附总量随床柱传质区高度的增加和3种离子初始质量浓度的升高而增加;在进水流速为4 m L/min时动态柱对离子的动态吸附容量最高,流速过大和过小都不利于复合吸附剂的动态吸附;在吸附剂填充高度15 cm,进水流速为4 m L/min时,动态柱对初始质量浓度分别为5,20和5 mg/L的F^(-),Fe^(2+),Mn^(2+)的最大动态吸附容量分别为1.567,7.008和1.615 mg/g。采用Thomas模型能较好描述Srp/HAP对F^(-),Fe^(2+),Mn^(2+)的吸附动力学特征。微观分析表明,吸附过程既有表面物理吸附,也有化学吸附,化学吸附主要表现为离子交换和表面络合作用。F^(-)部分取代HAP中的OH^(-),Fe^(2+)和Mn^(2+)则取代Srp中的Mg^(2+),使得F^(-),Fe^(2+),Mn^(2+)在复合颗粒表面的赋存状态主要以Fe_(3)Si_(2)(OH)_(4)O_(5),Mn_(3)Si_(2)(OH)_(4)O_(5),Ca_(5)(PO_(4))_(3)F化合物存在,另外HAP晶体表面的PO_(4)^(3-)与Fe^(2+)和Mn^(2+)也可能发生络合作用。蛇纹石负载羟基磷灰石复合颗粒可作为矿区处理含氟、铁、锰离子地下水的优良吸附剂。

To address the problem of excessive fluorine,iron,and manganese pollution associated with groundwater in mining areas,a composite adsorbent of serpentine-loaded hydroxyapatite(Srp/HAP)was prepared using a wet chemical co-precipitation method,and the synchronous adsorption performance of Srp/HAP on F^(-),Fe^(2+),and Mn^(2+)was investigated using dynamic adsorption tests to examine the effects of adsorption bed height,flow rate,and inlet water concentration on the penetration process.Adams-Bohart and Thomas model fitting and microscopic characterization by SEM,EDS,XRD,BET,and FT-IR were used to analyze the adsorption mechanism of Srp/HAP on F^(-),Fe^(2+),and Mn^(2+).The results show that the prepared Srp/HAP composite adsorbent particles are compact,which not only has a sheetlike curled structure on the surface of Srp,but also solves the problem of agglomeration on the surface of HAP.After loading,the specific surface area and pore volume of the particles are significantly increased,and they have a better surface.The pore structure facilitates the simultaneous adsorption and removal of fluorine,iron and manganese.The total adsorption volume of the adsorption column increases with the increase in the height of the bed column’s mass transfer zone and the initial concentration of the three ions.The dynamic column has the highest dynamic adsorption capacity for the ions at a feed water flow rate of 4 ml/min.Additionally,the large and small flow rates are not conducive to the dynamic adsorption of the composite adsorbent.When the adsorbent filling height is 15 cm and the inlet water flow rate is 4 m L/min,the dynamic column has the maximum dynamic adsorption capacity of F^(-),Fe^(2+)and Mn^(2+)with initial concentrations of 5,20,and 5 mg/L are respectively 1.567,7.008 and 1.615 mg/g.The adsorption kinetic characteristics of F^(-),Fe^(2+)and Mn^(2+)by Srp/HAP can be better described by the Thomas model.Microscopic analysis shows that the adsorption process includes surface physical adsorption and chemical adsorption,and chemical adsorption is mainly manifested by ion exchange and surface complexation.F^(-)partly replaces OH-in HAP,Fe^(2+)and Mn^(2+)replace Mg^(2+)in Srp,so that F^(-),Fe^(2+)and Mn^(2+)are mainly present on the surface of composite particles as Fe_(3)Si_(2)(OH)_(4)O_(5),Mn_(3)Si_(2)(OH)_(4)O_(5),Ca_(5)(PO_(4))_(3)F compounds exist,and PO43-on the surface of HAP crystals may also complex with Fe^(2+)and Mn^(2+).The serpentine-loaded hydroxyapatite composite particles can be used as excellent adsorbents for the treatment of groundwater containing fluorine,iron,and manganese ions in mining areas.